1 3/4 lbs. sirloin steak (look for thicker steaks), cut into 1 1/4 inch pieces
8 oz of button or cremini mushrooms, halved (unless small, keep whole)
3 bell peppers (1 red, 1 green, 1 yellow), each cut into 1 1/4-inch pieces
1 large red onion, diced into chunks (about 1 1/4-inch)
1 tablespoon olive oil, plus more for brushing grill grates
Salt and freshly ground black pepper
1/2 tablespoon garlic powder
10 wooden skewers sticks soaked in water for at least 30 minutes
Combine all marinade ingredients in a mixing dish and whisk to combine.
Place the steak in a gallon-size resealable bag for the kebabs. Pour the marinade over the steak and seal the bag while pressing out any air. Allow to marinate in the refrigerator 3 – 6 hours.
Preheat a grill, preferably gas, to about 425°F (about halfway through preheating if using charcoal).
Onion and cucumber are placed on a cutting board with the greens, then drizzled with oil and lightly tossed to cover.
Sprinkle salt and pepper over the veggies, then sprinkle with garlic powder. To make kebabs, lay the steak and vegetables on top of each other in a particular order, trying to fit 4 steak pieces on each kebab (I like to layer two onion slices together).
Brush the grill grates with oil. Grill the kebabs, turning them occasionally, until the center of the steak is cooked to medium doneness, about 8-9 minutes. Serve warm.